Annealing is the well known art of heat treating metals and is used to temper strands of metal such as wire or cable. The early art introduced batches of product into an oven for annealing but the process was slow and expensive. Continuous processes such as those shown in U.S. Pat. Nos. 1,993,400 and 2,726,971 were developed to continuously anneal wire by passing it along a series of rollers which apply electric current to the advancing wire to heat it as desired. A similar process for annealing cable is taught by U.S. Pat. No. 3,746,582. Originally, the rollers comprised sheaves having a groove in which the advancing strand traveled. It was found that the strand quickly wore out the sheaves because of continuous abrasion so replaceable sheave inserts such as the one shown in West German Pat. No. DT 25 20 161 were developed.
The insert is normally an endless flat strip forming the base of the groove while the flange portions form the side walls. Although the replacable insert decreases wear on the sheaves somewhat, sheave wear has remained unacceptably high until the present invention because the strand had no propensity to remain in contact only with the insert. Instead, the strand normally moved to one side and began to wear the sheave wall. In addition to having no tendency to remain centered on the insert surface, the strand even if not a magnetic material is often actually attracted to one side by the eddy current fields which are influenced by the mass of the annealer structure.
Where by chance the strand remains in contact only with the insert, an abrasion in the insert is relatively quickly worn and the insert is soon scared by an increasingly deep rut. Thus, in addition to wearing out the inner flange surfaces of the sheaves, the strand quickly wears out the insert which is designed to receive the bulk of the wear. Another problem is arcing which causes burn pits to the strand and to the insert and sheaves. The present invention solves the insert and sheave wear and most arcing problems by providing an annealing apparatus comprising a wide annealer band which is continuously traversed by the strand being annealed, extends the life of the band, and substantially eliminates detrimental arcing.